@CartoonSteve - like John K. said, the newest version of the free Quicktime Player (v 10.0) is terrible. Apple ruined it , just like they ruined iMovie . Download an older version of Quicktime Player like 7.6 (try here: http://mac.oldapps.com/quicktime.php ) or even better get Quicktime PRO which has a lot of advanced features for editing and exporting QT movies. http://store.apple.com/us/product/D3380Z/A

Also, about using Quicktime to view QT movies in a browser window: try using the Firefox browser instead of Safari. If you have Quicktime 7 installed then Firefox will still use the older QT 7 plug-in to play QT movies in the browser window, but Safari automatically defaults to the newer QT Player v. 10 plug-in (the bad one). Seems like Chrome also defaults to a newer version of the QT plug-in, so you can't step through the movies like in Firefox. Use Firefox version 3.6.16 on a Mac because in the new Firefox 4.0 for Mac the Quicktime Plug-in crashes frequently. (this is as of current date, April 23, 2011 -- hopefully in the near future Firefox will fix the issue with the QT plug-in crashing).

If you are looking for an older version of Firefox or older version of almost any app look here: http://mac.oldapps.com/